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Biomedical subjects

G Grizard

Publications and source records attributed to G Grizard.

At least 37 records · Page 2Linked to original sources
PubMed1992

Changes in carnitine and acetylcarnitine in human semen during cryopreservation.

L-Carnitine and acetylcarnitine concentrations were determined in spermatozoa and seminal plasma from 15 men, in both fresh ejaculate and frozen-thawed semen with cryoprotective medium. Sperm motility was also evaluated. In fresh samples, the levels of carnitine and acetylcarnitine in seminal plasma were comparable whereas in spermatozoa, acetylcarnitine predominated. Cryopreservation did not change the carnitine and acetylcarnitine levels in seminal plasma nor the carnitine concentration in spermatozoa; by contrast, the acetylcarnitine level in spermatozoa was decreased in 14 cases (110 +/- 8 versus 210 +/- 20 nmol/10(8) cells). This decrease in acetylcarnitine content was greater during semen dilution in cryoprotectant than after the freezing/thawing process. Motility was also decreased in all cases after the freezing/thawing process. These results suggest that acetylcarnitine recovery in spermatozoa is further evidence of the deleterious effect of the cryoprotective medium in the cryopreservation of semen.

Acetylcarnitine↗
PubMed1992

Influence of rat testicular macrophages on Leydig cell function in vitro.

The influence of co-cultures of rat testicular macrophages and Leydig cells (LC) on LC morphology and steroidogenesis was investigated with and without macrophage stimulation by a bacterial lipopolysaccharide (LPS). LC showed an elongated form in the presence of stimulated testicular macrophages. In the presence of non-stimulated testicular macrophages a significant inhibition of testosterone production was observed (decrease of 33%) from 48 h in co-culture while an increase of 16% was obtained at the same culture time, after stimulation of macrophages by LPS. When LC were treated with testicular macrophage-conditioned media (MCM) obtained from LPS-treated macrophages, they became fusiform and there was stimulation (78%) of steroid production. After human FSH stimulation (1-1000 mIU ml-1), MCM from testicular macrophages was no more effective in enhancing testosterone production by LC than was media from untreated LC. Similar experiments with LPS were conducted with macrophages of peritoneal origin. Peritoneal macrophages stimulated or not by LPS in co-cultures with LC or peritoneal MCM did not significantly modify testosterone production. However, these cells were able to modify LC morphology when LPS-MCM was added to LC-culture medium. The present results suggest strongly that testicular macrophage-LC interactions could be important in the control of LC steroidogenesis.

Animals↗
PubMed1992

Comparative study of the binding of prolactin and growth hormone by rabbit and human lung cell membrane fractions.

The specific binding capacities for human prolactin (hPRL) and human growth hormone (hGH) were examined in human lung membrane preparations at different developmental stages. A parallel study was carried out on rabbit lung preparations to compare binding parameters. Lung tissues were obtained from 15 fetuses of 16-38 weeks after spontaneous or therapeutic abortion and from 7 adults (lobar resection surgery). A histological study was systematically performed with a radial alveolar count in the fetuses with suspected hypoplasia. Binding analysis was performed on both intact membrane preparations and MgCl2-treated membranes, using [125I]hGH and [125I]hPRL as tracers. In the rabbit lung, specific [125I]hGH binding was found. Scatchard analysis revealed a single class of binding sites (affinity constant: 2.6 +/- 0.8 x 10(9) l/nmol and number of binding sites: 9.5 +/- 4.3 fmol/mg protein for adult rabbit; 1.85 +/- 0.5 x 10(9) l/nmol and 27.6 +/- 3.0 fmol/mg protein for 25-day-old rabbit fetuses, respectively). In contrast, [125I]hPRL did not specifically bind to lung membrane preparations. In the human lung, no consistent specific binding sites for [125I]hPRL or [125I]hGH (less than 0.5%/mg protein) were detected in adults and in 11 of the 15 fetuses. In 4 fetuses, little specific binding was observed (0.59-1.9%/mg protein) for [125I]hGH and (1.5%/mg protein) for [125I]hPRL. There was no correlation with histological lung structure. Our findings confirm the presence of specific binding sites for GH in the adult rabbit lung and demonstrate such binding in the fetal rabbit lung. In contrast, our results showed no significant binding for PRL and GH in the human lung, suggesting that these hormones do not play a direct physiological role in human lung growth and maturation.

Animals↗
PubMed1991

Insulin-like growth factor I (IGF-I) and insulin binding to erythrocytes of normal prepubertal children and adults.

Erythrocyte insulin-like growth factor I (IGF-I) and insulin receptors were characterized in 10 normal prepubertal children (5 girls and 5 boys) aged 4-11 yrs and 10 normal adults (4 women and 6 men) aged 32-47 yrs. erythrocytes were purified from 5 ml of blood by Ficoll-Paque gradient centrifugation. Reticulocytes count in the erythrocyte suspensions were lower than 1%. Insulin and IGF-I binding assays were performed simultaneously. Maximal percent binding of [125I] labelled IGF-I was significantly higher in prepubertal children than in adults (8.7 +/- 0.7% versus 6.2 +/- 0.5% at a concentration of 5 x 10(9) erythrocytes/ml). Scatchard analysis revealed the high affinity constant was better in prepubertal children (Ka = 4.6 +/- 1.3 nM-1 versus 1.8 +/- 0.2 nM-1), whereas the binding capacity was similar (5.8 +/- 1.1 versus 7.7 +/- 0.8 high affinity binding sites/cell). In both groups, unlabelled IGF-I inhibited tracer-binding half maximally at about 1 nM. Insulin was 100-fold less potent. In adults, specific binding of [125I] labelled IGF-I was higher in women (7.6 +/- 0.7%) than in men (5.3 +/- 0.4%). No significant difference was observed in maximal specific binding of [125I] labelled insulin between prepubertal children (8.2 +/- 0.5%) and adults (7.2 +/- 0.7%). In both groups, competition by unlabelled insulin for [125I] labelled insulin binding gave 50% displacement for approximately 0.25 nM and IGF-I was about 80-fold less potent. Both IGF-I and insulin binding parameters were not significantly correlated with plasma hormone levels. In prepubertal children, the high-affinity IGF-I receptors number decreased with increasing high-affinity insulin receptors number.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Insulin binding to Leydig cells and insulin levels in testicular interstitial fluid at different stages of development in the rat.

Binding of insulin to purified intact Leydig cells (LC) and LC membranes, and levels of insulin in plasma and testicular interstitial fluid (IF) were quantitatively evaluated in rats at three stages of development. Specific insulin binding to intact LC increased significantly with age. Scatchard analysis of the binding data always gave curvilinear plots; the number of high affinity binding sites/LC were 2590 +/- 514, 3977 +/- 701 and 8342 +/- 2039 at 21, 40 and 70 days respectively. When the results were expressed per micrograms membrane protein, the maximal specific insulin binding also increased between 21 and 40 days but did not significantly change thereafter. With ageing, insulin levels in testicular IF decreased (3.05 +/- 0.30, 2.48 +/- 0.22 and 1.66 +/- 0.13 micrograms/l in 21-, 40- and 70-day-old rats) whereas plasma insulin increased. Taken together, these results suggest (1) that the intratesticular environment in this hormone cannot be evaluated by plasma insulin levels--testicular IF insulin concentration is probably a better index and (2) that insulin may play a role in the development of LC function during sexual maturation.

Animals↗
PubMed1990

Glucocorticoid receptor concentrations in human lung at different growth stages.

We measured glucocorticoid receptor concentrations in human lung at different stages of alveolar growth. Lung tissue was obtained from 9 surgically aborted or stillborn fetuses of 15 to 28 weeks gestational age, and from 6 infants and children, aged 2 months to 9 years, after lobar resection or at autopsy. Samples were taken from macroscopically healthy areas. Lung histology was performed in all cases. The receptor assay was done by establishing saturation curves for labeled dexamethasone in the absence or presence of a hundredfold excess of unlabeled dexamethasone. Total binding capacity and the dissociation constant were calculated from the saturation curves by the method of Scatchard. The receptor concentration in the fetuses was high (182 +/- 88 fmol/mg prot.), irrespective of gestational age. The lowest concentration (35 fmol/mg prot.) was found in a fetus with pulmonary hypoplasia. In the infants and children the mean receptor concentration was significantly lower (14.6 +/- 9.9 fmol/mg prot.); these included a case of sudden death in which the parenchymal structure was normal.

Child↗
PubMed1989

Aromatase activity in purified Leydig cells from adult rat. Comparative effects of insulin, IGF-I, and hCG.

The comparative effects of insulin and IGF-I on aromatization in adult rat purified Leydig cells were examined to elucidate the mechanism of action of the peptides in testicular steroidogenesis. Aromatase activity was measured in short-time incubations, using the tritiated water release method with [1 beta-3H] and androstenedione as substrate. In the presence of varying concentrations of substrate, the apparent Km for androstenedione was 0.945 mol/l; treatment of cells with insulin, IGF-I and hCG markedly increased the apparent maximal velocity, without modifying Km; peptides were more potent in aromatase stimulation than hCG alone or in combination with either peptides. When related to time (0-4 h) and expressed as percent of control values, aromatase activity in the presence of insulin, IGF-I and/or hCG exhibited a significant and transient increase at 15-30 min. In order to clarify the nature of this early stimulation, the effects of dibutyryl cAMP, various antibiotics, and cytochalasin B on treated Leydig cells were analysed. Results indicated that insulin and IGF-I action on aromatization was not cAMP-dependent; peptides could intervene by increasing RNA and protein, but not DNA, synthesis; they were also effective in glucose transport. These data suggest that insulin and IGF-I are able to modulate aromatization in Leydig cells.

Animals↗
PubMed1988

Characterization of insulin binding and comparative action of insulin and insulin-like growth factor I on purified Leydig cells from the adult rat.

Insulin binding and insulin action were characterized in adult rat Leydig cells, purified on discontinuous Percoll gradients. Binding of [125I]-porcine insulin was found to be dependent on time, temperature, cell concentration and Leydig cell specific gravity. Competition relative to porcine insulin (100) was as follows: insulin-like growth factor I (IGF-I) : less than 1; proinsulin : 5; guinea-pig insulin : 2; hCG, ovine prolactin and bovine GH : 0. High and low affinity binding sites for insulin were identified on purified Leydig cells with Ka values of 1.2 X 10(9) and 0.3 X 10(8) M-1, with 10,300 and 34,000 binding sites per cells, respectively. Using primary cultures of Leydig cells in serum-free medium, the action of insulin on steroidogenesis was studied and compared with IGF-I action. Insulin and IGF-I used at 1-35 nM enhanced basal testosterone production in a dose-dependent manner; the effect was significant 4 h after administration. Insulin or IGF-I also potentiated the effect of hCG on steroidogenesis during short-term incubation (4 h). Insulin was shown to improve hCG responsiveness without modifying sensitivity to hCG. Moreover, neither cell number nor hCG-binding was altered by insulin, IGF-I or a combination of the two. Concomitant treatment with insulin and IGF-I at half-maximal and maximally effective doses, in the presence or absence of hCG, indicated that the two factors synergized in the stimulation of testosterone production via a common saturable mechanism.

Animals↗
PubMed1987

Testosterone, androstenedione, progesterone and 17 alpha-hydroxyprogesterone in plasma and testes of immature rats under basal conditions and after hCG stimulation. Effect of bilateral cryptorchidism.

Rats were made bilaterally cryptorchid at 21 days of age; sham-operated rats were used as controls. At 35 days, the animals were injected i.m. with saline or with 10 IU hCG. Progesterone, 17-hydroxyprogesterone, androstenedione and testosterone were measured in both testes and plasma under basal conditions and 2, 4, 8, 12, 24 and 72 h respectively after injection. The plasma levels and intratesticular contents of the steroids were generally lower in cryptorchid rats. The patterns of the steroid response to hCG were similar in both groups: in the testes and in the plasma, they increased acutely following hCG injection (except testicular androstenedione), then, after 72 h, returned to normal values in the plasma but remained higher than the basal values in the testes. These results suggest that there are no gross abnormalities in the testicular steroidogenic pathways and that the mechanism of action of hCG on the Leydig cells is unaltered in bilaterally cryptorchid immature rats.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Binding and degradation of 125I-glucagon by highly purified rat liver plasma membranes.

125I-glucagon binding and degradation were studied in highly purified plasma membranes from rat livers. Specific 125I-glucagon binding increased rapidly with time at 30 degrees C and reached a maximum between 30 and 120 min. At 120 min the labelled material present in the supernatants from incubation mixtures had extensively lost its ability to rebind to fresh membranes whatever the glucagon concentration. This impairment was not due to the release of a degradative activity into the incubation mixture, suggesting a membrane-mediated process. The presence of proteinase inhibitors (bacitracin/aprotinin) resulted both in an increase in specific 125I-glucagon binding to membranes and an improvement in the ability of the labelled material from the supernatant to rebind to fresh membranes. When analysed by Bio-Gel P-10 chromatography the loss in the ability of the labelled material in the supernatants to rebind to fresh membranes correlated with a decrease in the labelled material which eluted as 125I-glucagon from the column. Chromatographic analysis overestimated 125I-glucagon when compared to the radioreceptor assay. The labelled material extracted from membranes by Triton X-100 solubilization or dissociated from membranes after exposure to an excess of unlabelled glucagon mainly eluted as 125I-glucagon. However, a significant amount (20-30%) of the labelled material eluted in the low molecular weight region.

Animals↗
PubMed1986

Effect of human chorionic gonadotropin on luteinizing hormone and prolactin binding by testes of bilaterally cryptorchid rats.

This study investigates the ability of the testis in the cryptorchid state to bind luteinizing hormone (LH) and prolactin (Prl). For this purpose, rats were made bilaterally cryptorchid at 21 days of age; sham-operated rats were used as controls. At 56 days, the animals were injected with saline or with increasing doses of human chorionic gonadotropin (hCG: 1, 10 or 100 IU) and killed 8 or 24 h after injection. Cryptorchidism and injection of hCG did not alter plasma Prl levels. In cryptorchid rats, both LH and Prl binding expressed in pmol/testis were lower than in sham-operated controls (about 75% and 65%, respectively), but unchanged (LH binding) or increased (Prl binding) when expressed in pmol/g testis. In controls, 100 IU hCG induced a significant decrease in LH binding at 24 h. Prl binding was also significantly lower in controls injected with 100 IU hCG than in those injected with 1 or 10 IU hCG, at 8 h. In cryptorchid rats injected with 100 IU hCG, the LH binding fell 8 h and 24 h after injection; at 24 h, hCG reduced Prl binding. In conclusion, there was a considerable decrease in LH and Prl receptors in the abdominal testes. The negative regulation of these receptors in response to hCG was maintained, but at times and for doses which differed from those observed in scrotal testes.

Animals↗
PubMed1985

Seminal biochemistry and sperm characteristics in infertile men with bacteria in ejaculate.

Sperm examination, quantitative sperm culture, citric acid, acid phosphatase, and fructose were assayed in three groups of men: fertile controls without significant bacteriospermia (group I), infertile men with significant bacteriospermia; idiopathic infertile men (group II), and infertile men with varicocele (group III). Level of significance of bacteriospermia was greater than or equal to 10(4) germs/ml of ejaculate. In group II, motility and typical morphology percentages were lower, independently of the degree and the nature of bacteriospermia. Incidence of pathogenic bacteria was higher than in group III and linked to the degree of bacteriospermia. Fructose was unaltered in the two groups of infected men. No modification of prostatic markers was observed in any groups, except in group II, where they decreased when bacteriospermia was lower than 10(5) germs/ml and when biological pattern of semen evoked chronic prostatitis. Thus, the presence of germs in ejaculate alters the motility and the typical morphology percentages but does not result in any obvious modifications of biochemical markers of prostate and seminal vesicles. For idiopathic infertile men, it is suggested that the quantitative criterion of pathogenic bacteriospermia is a germ count greater than or equal to 10(5)/ml.

Acid Phosphatase↗
PubMed1983

Effects of bromocriptine on pituitary-testicular function in the rat: possible inhibition of in vitro production of androgen by Leydig cells.

The effect of bromocriptine (BR) on pituitary-testicular function has been investigated in vivo and in vitro in adult male rats. Testosterone production in vitro by collagenase- dispersed Leydig cells from 84-day-old rats was evaluated in the presence and absence of hCG and/or different doses of BR. In the presence of 1.5 X 10(-5) M BR, both basal and hCG-stimulated testosterone production were decreased whereas at lower doses BR was ineffective. In vivo 60-day-old rats were injected sc with BR (150 micrograms/rat or 750 micrograms/rat twice daily) or vehicle for 24 days. This treatment reduced the plasma level and pituitary content of prolactin, slightly increased the plasma levels of LH and FSH but did not affect pituitary gonadotrophin content. Irrespective of the dose of BR injected, plasma levels of androgen did not change, but with the large dose of BR a decrease in testicular content of testosterone (P = 0.05) was observed. In the same animals the number of LH/hCG receptors was significantly reduced, and the sensitivity of the isolated Leydig cells to hCG stimulation in vitro was reduced; however, both the basal secretion and the maximum testosterone response to hCG were unaffected. These results show impairment of pituitary-testicular function in BR-treated rats, either as a result of BR-induced hypoprolactinaemia or as a consequence of direct effects of BR on the Leydig cells.

Androgens↗
PubMed1983

Human frontal sweat rate and lactate concentration during heat exposure and exercise.

Output (Qsweat) and lactate concentration ( [L]sweat) in frontal sweat and blood lactate concentration ( [L]blood) were monitored in three male volunteers: one sedentary (S), one fit (F), and one very fit (VF). Measurements were made under three sweating conditions: 1) heat exposure to infrared radiation (IR) at rest for 25 min at 45 degrees C; 2) bicycle exercise at constant relative maximal aerobic power (87 +/- 2% MAP) for 25 min (Cst EX) at 23 degrees C; and 3) bicycle exercise at increasing work loads (from 60-95% MAP) in four or five successive 5-min steps (Incr EX) at 23 degrees C. Comparison of these data showed that under the above three conditions 1) Qsweat of S was lower than that of F and VF; and 2) changes in [L]sweat were different: in IR and Cst EX, [L]blood remained constant, and [L]sweat decreased with heat load duration similarly in the three subjects (the slopes of the two curves were not significantly different); at Incr Ex, [L]blood increased and [L]sweat remained constant in S, F, and VF (21.71 +/- 0.85, 16.75 +/- 0.99, 12.83 +/- 0.45 (SE) mM, respectively). It was suggested that the high [L]blood and increased adrenergic stimulation observed in Incr Ex could act on [L]sweat in relation to the physical fitness level.

Adult↗
PubMed1982

Testicular receptors of human chorionic gonadotrophin in adult men. Binding and degradation of the hormone.

Binding and degradation of human chorionic gonadotrophin (hCG) to testicular tissue obtained by biopsy from 9 men with gonadal disorders were investigated. Vacant hCG receptors were assayed in partially purified testicular homogenates using [125I]hCG (radioiodinated with chloramine T). Degradation of [125I]hCG during exposure to human testicular preparations was measured in terms of the ability of supernatants to specifically bind to rat testicular receptors. Binding of [125]hCG was time and temperature dependent. At 37 degrees C, a maximum was reached at 8 h. It was also found to be a saturable process with respect to homogenate and hormone concentrations. Association constants and number of binding sites determined in 9 men, using Scatchard plot and saturation curve analysis ranged, respectively, from 0.2 to 1.8 x 10(10) M-1 and from 92 to 3427 fmol/g testis or 7 to 380 fmol/mg protein. Degradation of [125I]hCG increased with temperature and time of exposure to human testicular homogenate. It increased also with increasing human testicular homogenate concentration and substrate concentrations. For a similar concentration of [125I]hCG, per cent of degraded hormone ranged from 32 to 57, according to the subjects. These results show that human testicular homogenates are capable of binding and degrading hCG in vitro. Biological and physiological implications of degradation for hormone binding are discussed.

Adult↗
PubMed1982

[Inhibition of prolactin secretion and androgenic function in the adult male rat].

The effects of bromocriptine induced hypoprolactinemia on the testicular function were studied in adult rats. Bromocriptine treatment (1500 micrograms/day for 24 days) reduced serum and pituitary Prolactin levels, indicating a decrease in prolactin secretion and synthesis. No change in reproductive organ weights was seen in treated animals. Hypoprolactinemia had no effect on plasma testosterone or androstenedione levels and testicular androstenedione content, but decreased significantly testicular testosterone content. These findings indicated that experimental hypoprolactinemia induced a decrease in testicular testosterone content without affecting androgens levels.

Androgens↗
PubMed1981

[Validity of radioimmunoassay for blood and pituitary prolactin in the male rat. Effect of bromocriptine and thyrotropin-releasing hormone].

Validity of a radioimmunoassay for rat prolactin (PRL) in serum and pituitary is analysed in adult male rats. Data are presented bearing on the accuracy, precision and sensitivity of the method. Serum levels and pituitary content are respectively ranged from 2.56 to 28.03 ng PRL RP2 ml-1 and from 7.36 to 21.44 microgram PRL RP2 per gland in intact animals. Treatment with bromocriptine (10 days) results in a decrease of serum PRL levels and pituitary PRL contents. In progesterone-estradiol benzoate pretreated rats, serum PRL levels are increased 20 min after the injection of TRH.

Animals↗